Description

Returns one or more bands of an existing raster as a new raster. Useful for building new rasters from existing rasters or export of only selected bands of a raster or rearranging the order of bands in a raster. If no band is specified, band 1 is assumed. Used as a helper function in various functions such as for deleting a band.

For the nbands as text variant of function, the default delimiter is , which means you can ask for '1,2,3' and if you wanted to use a different delimeter you would do ST_Band(rast, '1@2@3', '@'). For asking for multiple bands, we strongly suggest you use the array form of this function e.g. ST_Band(rast, '{1,2,3}'::int[]); since the text list of bands form may be removed in future versions of PostGIS.

Availability: 2.0.0

Examples

-- Make 2 new rasters: 1 containing band 1 of dummy, second containing band 2 of dummy and then reclassified as a 2BUI
SELECT ST_NumBands(rast1) As numb1, ST_BandPixelType(rast1) As pix1, 
 ST_NumBands(rast2) As numb2,  ST_BandPixelType(rast2) As pix2
FROM (
    SELECT ST_Band(rast) As rast1, ST_Reclass(ST_Band(rast,3), '100-200):1, [200-254:2', '2BUI') As rast2
        FROM dummy_rast
        WHERE rid = 2) As foo;
        
 numb1 | pix1 | numb2 | pix2
-------+------+-------+------
     1 | 8BUI |     1 | 2BUI
					

-- Return bands 2 and 3. Using array cast syntax
SELECT ST_NumBands(ST_Band(rast, '{2,3}'::int[])) As num_bands
    FROM dummy_rast WHERE rid=2;
    
num_bands
----------
2
    
-- Return bands 2 and 3. Use array to define bands
SELECT ST_NumBands(ST_Band(rast, ARRAY[2,3])) As num_bands
    FROM dummy_rast 
WHERE rid=2;
					

original (column rast)

dupe_band

sing_band

--Make a new raster with 2nd band of original and 1st band repeated twice,
and another with just the third band
SELECT rast, ST_Band(rast, ARRAY[2,1,1]) As dupe_band,  
	ST_Band(rast, 3) As sing_band 
FROM samples.than_chunked 
WHERE rid=35;							
					

See Also

ST_AddBand, ST_NumBands, ST_Reclass, Chapter 9, Raster Reference